This package from SynoCommunity did not work on my DS409slim. I wrote a little summary of the steps I took by myself to get it running. If anyone's interested: http://www.blackv.tk/general/setting-up-bittorrent-sync-as-a-daemon-on-synology-nas/
I wrote a little post about my experience setting it up on my DiskStation and also implement propper start-on-boot. You can read it up here: http://www.blackv.tk/general/setting-up-bittorrent-sync-as-a-daemon-kind-of-on-synology-nas/